1. Field of the Invention
The invention relates to a method and apparatus for controlling reproduction speed of an optical disk.
2. Background of the Related Art
For read-out of information recorded on an optical disk, such as compact disc (CD) or digital versatile disc (DVD), an optical disk reproducing apparatus irradiates a laser beam onto the optical disk through an objective lens and collects the reflected beam while rotating the optical disk at an appropriate speed using a spindle motor. The rotational speed of the optical disk determines the data reproduction speed, which is controlled by a servo control circuit that provides drive voltage to the spindle motor.
With the advancement of servo technology, the access speed of an optical disk reproducing apparatus has improved rapidly. As a result, data recorded on an optical disk can be retrieved more rapidly than the normal 1× speed.
Maximum-speed data reproduction requires maximum-speed rotation of the optical disk, which entails more vibration and noise generated by the rotation mechanism. If a host computer that requested data read-out from an optical disk does not take the data temporarily stored in a buffer on time, the optical disk reproducing apparatus should conduct backward track jumps, in which case the benefit of the maximum-speed rotation disappears.
The optical disk reproducing apparatus, therefore, performs data read-out not with the maximum rotational speed but with a rather lower speed with a view to decreasing noise. For example, an optical disk reproducing apparatus with maximum rotational speeds approximately ˜24×-52× (rotational speed expressed in terms of CLV speed) in the CAV mode rotates the optical disk with ˜20×-48× speeds, ˜4× lower than the maximum speed at each location, as shown in FIG. 1.
Users sometimes execute a test program, such as a Landmark test (bench mark) program, to measure the performance of their optical disk drives installed in their PCs. When executed, the test program issues disk read commands to the optical disk drive for measuring data read performance. The optical disk drive responsive to the commands performs data read-out at a speed rather lower than the maximum speed. Because the optical disk drive with maximum CAV speeds of ˜24×-52× performs data read-out with speeds of ˜20×-48×, the performance index obtained by the test program does not reflect the actual maximum performance of the optical disk drive.
The performance index obtained by the test program, which is lower than the expected value, makes users doubt the performance of their disk drives, which may lead to unnecessary requests for repair service.